During short-circuit breaking, a truck-mounted high-voltage circuit breaker is subjected to large ejection forces. The forces cause deflection of the breaker poles and attempt to move the truck in the direction of travel. If the movement becomes larger than the contact action, the breaker breaks down.
Patent EP-A-0 603 762 specification describes a special capture contact device adapted to eliminate the above-mentioned problems with withdrawable high-voltage apparatus. In this contact device, the current forces generated when the apparatus is traversed by short-circuit current are utilized to block the plug-in contacts of the apparatus in the operating position, thus preventing the risk of arcing between the contacts.